Torque motor-drive spool valves are well known in the art including those which operate through the utilization of a rotary torque motor having a drive member extending from the rotor thereof into contact with the spool valve to directly reciprocate the spool valve within a bore provided in the valve housing to thereby control the flow of fluid from a source thereof to the load in response to electrical signals applied to the drive motor. Typical of such direct drive servovalves is that illustrated in U.S. Pat. No. 4,793,377 issued Dec. 27, 1988 to Larry E. Haynes et al. The invention described and claimed herein is an improvement over the direct drive servovalve disclosed in U.S. Pat. No. 4,793,377 and therefore the disclosure of U.S. Pat. No. 4,793,377 is incorporated herein by this reference.
Other prior art known to applicant is U.S. Pat. Nos. 4,197,474; 2,769,943; 2,697,016; 4,452,423; 4,339,737; and, 4,702,123 as well as Canadian Patent 601808 issued Jul. 19, 1960 and United Kingdom Patent 1521668 issued Aug. 16, 1978. It is desirable in direct drive servovalves that the interconnection between the rotor shaft and the bearings which carry the rotor shaft be such that there is little or no back lash or radial play therein. To create a relatively stiff assembly and eliminate such radial play, it has been common to load the motor bearings by placing shims wave springs or the like in the structure to constantly preload the bearings and eliminate such radial play or sloppiness. The necessity of including such shims, wave springs or the like increases the cost of the motor as well as the cost of the manufacture and assembly of the same.